• Molecules and Cells
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• v.37 no.7
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• pp.511-517
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• 2014

MicroRNAs are non-coding short (~23 nucleotides) RNAs that mediate post-transcriptional regulation through sequence-specific gene silencing. The role of miRNAs in neuronal development, synapse formation and synaptic plasticity has been highlighted. However, the role of neuronal activity on miRNA regulation has been less focused. Neuronal activity-dependent regulation of miRNA may finetune gene expression in response to synaptic plasticity and memory formation. Here, we provide an overview of miRNA regulation by neuronal activity including high-throughput screening studies. We also discuss the possible molecular mechanisms of activity-dependent induction and turnover of miRNAs.

• Journal of Korean Neurosurgical Society
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• v.53 no.2
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• pp.72-76
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• 2013

Objective : Cerebral aneurysm (CA) is an important acquired cerebrovascular disease that can cause catastrophic results. MicroRNAs (miRNAs) are small non-coding RNAs, playing essential roles in modulating basic physiologic and pathological processes. Currently, evidences have been established about biologic relationship between miRNAs and abdominal aortic aneurysms. However, biologic roles of miRNAs in CA formation have not been explained yet. We employed microarray analysis to detect and compare miRNA expression profiles in late stage of CA in rat model. Methods : Twenty-six, 7-week-old male Sprague-Dawley rats underwent a CA induction procedure. The control animals (n=11) were fed a normal diet, and the experimental animals (n=26) were fed a normal diet with 1% normal saline for 3 months. Then, the rats were sacrificed, their cerebral arteries were dissected, and the five regions of aneurysmal dilation on the left posterior communicating artery were cut for miRNA microarrays analysis. Six miRNAs (miRNA-1, miRNA-223, miRNA-24-1-5p, miRNA-551b, miRNA-433, and miRNA-489) were randomly chosen for validation using real-time quantitative PCR. Results : Among a set of differentially expressed miRNAs, 14 miRNAs were over-expressed more than 200% and 6 miRNAs were down-expressed lower than 50% in the CA tissues. Conclusion : The results show that miRNAs might take part in CA formation probably by affecting multiple target genes and signaling pathways. Further investigations to identify the exact roles of these miRNAs in CA formation are required.

• IMMUNE NETWORK
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• v.16 no.4
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• pp.249-255
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• 2016

Exogenous nucleic acids induce an innate immune response in mammalian host cells through activation of the retinoic acid-inducible gene I (RIG-I). We evaluated RIG-I protein for RNA binding and ATPase stimulation with RNA ligands to investigate the correlation with the extent of immune response through RIG-I activation in cells. RIG-I protein favored blunt-ended, double-stranded RNA (dsRNA) ligands over sticky-ended dsRNA. Moreover, the presence of the 5'-triphosphate (5'-ppp) moiety in dsRNA further enhanced binding affinity to RIG-I. Two structural motifs in RNA, blunt ends in dsRNA and 5'-ppp, stimulated the ATP hydrolysis activity of RIG-I. These structural motifs also strongly induced IFN expression as an innate immune response in cells. Therefore, we suggest that IFN induction through RIG-I activation is mainly determined by structural motifs in dsRNA that increase its affinity for RIG-I protein and stimulate ATPase activity in RIG-I.

• International Journal of Oral Biology
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• v.43 no.4
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• pp.223-230
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• 2018

Exosomes are Nano-sized lipid vesicles secreted from mammalian cells containing diverse cellular materials such as proteins, lipids, and nucleotides. Multiple lines of evidence indicate that in saliva, exosomes and their contents such as microRNAs (miRNAs) mediate numerous cellular responses upon delivery to recipient cells. The objective of this study was to characterize the different expression profile of exosomal miRNAs in saliva samples, periodically isolated from a single periodontitis patient. Unstimulated saliva was collected from a single patient over time periods for managing periodontitis. MicroRNAs extracted from each phase were investigated for the expression of exosomal miRNAs. Salivary exosomal miRNAs were analyzed using Affymetrix miRNA arrays and prediction of target genes and pathways for its different expression performed using DIANA-mirPath, a web-based, computational tool. Following the delivery of miRNA mimics (hsa-miR-4487, -4532, and -7108-5p) into human gingival fibroblasts, the expression of pro-inflammatory cytokines and activation of the MAPK pathway were evaluated through RT-PCR and western blotting. In each phase, 13 and 43 miRNAs were found to be differently expressed $({\mid}FC{\mid}{\geq}2)$. Among these, hsa-miR-4487 $({\mid}FC{\mid}=9.292005)$ and has-miR-4532 $({\mid}FC{\mid}=18.322697)$ were highly up-regulated in the clinically severe phase, whereas hsa-miR-7108-5p $({\mid}FC{\mid}=12.20601)$ was strongly up-regulated in the clinically mild phase. In addition, the overexpression of miRNA mimics in human gingival fibroblasts resulted in a significant induction of IL-6 mRNA expression and p38 phosphorylation. The findings of this study established alterations in salivary exosomal miRNAs which are dependent on the severity of periodontitis and may act as potential candidates for the treatment of oral inflammatory diseases.

• Molecules and Cells
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• v.38 no.11
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• pp.959-965
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• 2015

Inducible and reversible gene silencing in desired types of cells is instrumental for deciphering gene functions using cultured cells or in vivo models. However, efficient conditional gene knockdown systems remain to be established. Here, we report the generation of an inducible expression system for short hairpin RNA (shRNA) targeted to PTEN, a well-documented dual-specificity phosphatase involved in tumor suppression and ontogenesis. Upon induction by doxycycline (DOX), the reverse tetracycline transcriptional activator (rtTA) switched on the concomitant expression of GFP and a miR-30 precursor, the subsequent processing of which released the embedded PTEN-targeted shRNA. The efficacy and reversibility of PTEN knockdown by this construct was validated in normal and neoplastic cells, in which PTEN deficiency resulted in accelerated cell proliferation, suppressed apoptosis, and increased invasiveness. Transgenic mice harboring the conditional shRNA-expression cassette were obtained; GFP expression and concurrent PTEN silencing were observed upon ectopic expression of rtTA and induction with Dox. Therefore, this study provides novel tools for the precise dissection of PTEN functions and the generation of PTEN loss of function models in specific subsets of cells during carcinogenesis and ontogenesis.

• BMB Reports
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• v.52 no.3
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• pp.196-201
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• 2019

The Alu element, the most abundant transposable element, is transcribed to Alu RNA. We hypothesized that the PIWI protein regulates the expression of Alu RNA in retinal pigment epithelial (RPE) cells, where accumulated Alu RNA leads to macular degeneration. Alu transcription was induced in RPE cells treated with $H_2O_2$. At an early stage of oxidative stress, PIWIL4 was translocated into the nucleus; however, subsequently it was sequestered into cytoplasmic stress granules, resulting in the accumulation of Alu RNA. An elevated amount of Alu RNA was positively correlated with the disruption of the epithelial features of RPE via induction of mesenchymal transition. Therefore, we suggest that oxidative stress causes Alu RNA accumulation via PIWIL4 sequestration into the cytoplasmic stress granules.

• Journal of Life Science
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• v.24 no.3
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• pp.323-328
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• 2014

MicroRNAs comprise a family of small noncoding RNAs that modulate physiological processes, including adipogenesis. MicroRNA-17 (miR-17) promotes adipocyte differentiation and enhances lipid accumulation. The transcriptional regulation of miR-17 during adipogenesis remains unknown. In this study, we investigated whether miR-17 is a target of peroxisome proliferator-activated receptor ${\gamma}$ ($PPAR{\gamma}$), which is a key regulator of adipogenesis. The levels of miR-17 and the expression of $PPAR{\gamma}$ increased after the induction of adipocyte differentiation. Three putative peroxisome proliferator response elements (PPREs) were identified in the miR-17 promoter region. Using chromatin immunoprecipitation and luciferase reporter assays, we observed the interaction of $PPAR{\gamma}$ with the miR-17 promoter. Mutagenesis experiments showed that the -677/-655 region of the miR-17 promoter could function as a PPRE site. These results suggest that $PPAR{\gamma}$ is essential for transcriptional activation of the miR-17 gene, thereby contributing to understanding the molecular mechanism of adipogenesis in adipocytes.

• BMB Reports
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• v.53 no.11
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• pp.605-610
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• 2020

Skeletal myogenesis is a complex process that is finely regulated by myogenic transcription factors. Recent studies have shown that saturated fatty acids (SFA) can suppress the activation of myogenic transcription factors and impair the myogenic differentiation of progenitor cells. Despite the increasing evidence of the roles of miRNAs in myogenesis, the targets and myogenic regulatory mechanisms of miRNAs are largely unknown, particularly when myogenesis is dysregulated by SFA deposition. This study examined the implications of SFA-induced miR-183-5p on the myogenic differentiation in C2C12 myoblasts. Long-chain SFA palmitic acid (PA) drastically reduced myogenic transcription factors, such as myoblast determination protein (MyoD), myogenin (MyoG), and myocyte enhancer factor 2C (MEF2C), and inhibited FHL1 expression and myogenic differentiation of C2C12 myoblasts, accompanied by the induction of miR-183-5p. The knockdown of FHL1 by siRNA inhibited myogenic differentiation of myoblasts. Interestingly, miR-183-5p inversely regulated the expression of FHL1, a crucial regulator of skeletal myogenesis, by targeting the 3'UTR of FHL1 mRNA. Furthermore, the transfection of miR-183-5p mimic suppressed the expression of MyoD, MyoG, MEF2C, and MyHC, and impaired the differentiation and myotube formation of myoblasts. Overall, this study highlights the role of miR-183-5p in myogenic differentiation through FHL1 repression and suggests a novel miRNA-mediated mechanism for myogenesis in a background of obesity.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.8
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• pp.3363-3368
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• 2014

Background: Curcumin, a phenolic compound extracted from the rhizomes of Curcuma longa, has shown cytotoxic effects against a variety of cancers. The aim of this study was to identify potential microRNA (miRNA) mediators of the anticancer effects of curcumin in ovarian cancer cells. Materials and Methods: SKOV3 ovarian cancer cells were treated with curcumin ($10-60{\mu}M$) and miR-9 expression, cell proliferation, and apoptosis were assessed. The effects of miR-9 depletion on curcumin-mediated growth suppression were also examined. Phosphorylation of Akt and forkhead box protein O1 (FOXO1) was measured in cells with miR-9 overexpression or curcumin treatment. Results: Curcumin caused a significant and dose-dependent increase of miR-9 expression in SKOV3 cells, while significantly impeding cell proliferation and stimulating apoptosis. Depletion of miR-9 significantly (p<0.05) attenuated the growth-suppressive effects of curcumin on SKOV3 cells, coupled with reduced percentages of apoptotic cells. In contrast, overexpression of miR-9 significantly enhanced the cleavage of caspase-3 and poly(ADP-ribose) polymerase and promoted apoptotic death in SKOV3 cells. Western blot analysis showed that both miR-9 overexpression and curcumin similarly caused a significant (p<0.05) decline in the phosphorylation of Akt and FOXO1, compared to untreated cells. Conclusions: The present study provided evidence that curcumin exerts its cytotoxic effects against SKOV3 ovarian cancer cells largely through upregulation of miR-9 and subsequent modulation of Akt/FOXO1 axis. Further studies are needed to identify direct targets of miR-9 that mediate the anticancer effects of curcumin in ovarian cancer cells.

• Archives of Pharmacal Research
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• v.29 no.12
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• pp.1154-1157
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• 2006

The ermK gene from Bacillus lichenformis encodes an inducible rRNA methylase that confers resistance to the macrolide-lincosamide-streptogramin B antibiotics. The ermK mRNA leader sequence has a total length of 357 nucleotides and encodes a 14-amino acid leader peptide together with its ribosome binding site. The secondary structure of ermK leader mRNA and a leader peptide sequence have been reported as the elements that control expression. In this study, the contribution of specific leader peptide amino acid residues to induction of ermK was studied using the PCR-based megaprimer mutation method. ermK methylases with altered leader peptide codons were translationally fused to E. coli ${\beta}-galactosidase$ reporter gene. The deletion of the codons for Thr-2 through Ser-4 reduced inducibility by erythromycin, whereas that for Thr-2 and His-3 was not. The replacement of the individual codons for Ser-4, Met-5 and Arg-6 with termination codon led to loss of inducibility, but stop mutation of codon Phe-9 restored inducibility by erythromycin. Collectively, these findings suggest that the codons for residue 4, 5 and 6 comprise the critical region for induction. The stop mutation at Leu-7 expressed constitutively ermK gene. Thus, ribosome stalling at codon 7 appears to be important for ermK induction.